U.S. patent number 10,619,037 [Application Number 15/819,865] was granted by the patent office on 2020-04-14 for roofing compositions comprising linear low density polyethylene.
This patent grant is currently assigned to Johns Manville. The grantee listed for this patent is JOHNS MANVILLE. Invention is credited to Jawed Asrar, Jordan Kortmeyer, Lichih R Peng, Lance Wang.
United States Patent |
10,619,037 |
Peng , et al. |
April 14, 2020 |
Roofing compositions comprising linear low density polyethylene
Abstract
Provided is a polymer blend composition comprising linear low
density polyethylene, a propylene polymer generally having rubber
dispersed therein, and a combination of a propylene copolymer and
an ethylene copolymer. In one embodiment, there is provided a
polymer blend composition comprising 15 to 75 weight percent of a
propylene polymer having from 10-60% crystallinity, 30-50 weight
percent of a linear low density polyethylene, and a combination of
the propylene copolymer and the ethylene copolymer comprising the
remainder of the composition.
Inventors: |
Peng; Lichih R (Littleton,
CO), Kortmeyer; Jordan (Parker, CO), Wang; Lance
(Parker, CO), Asrar; Jawed (Englewood, CO) |
Applicant: |
Name |
City |
State |
Country |
Type |
JOHNS MANVILLE |
Denver |
CO |
US |
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Assignee: |
Johns Manville (Denver,
CO)
|
Family
ID: |
64664461 |
Appl.
No.: |
15/819,865 |
Filed: |
November 21, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190153201 A1 |
May 23, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E04D
5/06 (20130101); E04D 5/08 (20130101); C08L
23/142 (20130101); C08L 23/0815 (20130101); C08L
23/142 (20130101); C08L 23/0815 (20130101); C08L
23/14 (20130101); C08L 23/16 (20130101); C08L
23/0815 (20130101); C08L 23/14 (20130101); C08L
23/142 (20130101); C08L 23/16 (20130101); C08L
2205/035 (20130101); C08L 2201/02 (20130101); C08L
2205/08 (20130101); C08L 2207/02 (20130101); C08L
2205/02 (20130101); C08L 2207/066 (20130101) |
Current International
Class: |
C08L
23/08 (20060101); C08L 23/14 (20060101); E04D
5/06 (20060101); E04D 5/08 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO-2016137558 |
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Sep 2016 |
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WO |
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Primary Examiner: Uselding; John E
Attorney, Agent or Firm: Touslee; Robert D.
Claims
What is claimed is:
1. A membrane composition comprising: a) from about 40 wt % to 75
wt % of a polymer blend composition comprising; (i) 15-75 wt % of a
propylene polymer having from 10-60% crystallinity and rubber
dispersed therein; (ii) 30-50 wt % of a linear low density
polyethylene; and (iii) 5-20 wt % of a combination of a propylene
copolymer and an ethylene copolymer; b) at least one flame
retardant; c) at least one ultraviolet stabilizer; and d) at least
one pigment.
2. The membrane composition of claim 1, wherein the flame retardant
comprises 20-40 wt % of the composition.
3. The membrane composition of claim 1, wherein the pigment
comprises from 4 to 6 wt % of the composition.
4. The membrane composition of claim 1, wherein the pigment
comprises TiO.sub.2.
5. A roofing membrane comprising the membrane composition of claim
1.
6. A roof comprising the roofing membrane of claim 5.
7. A method of preparing a thermoplastic polyolefin film, the
method comprising forming a thermoplastic polyolefin film from the
composition of claim 1.
8. The membrane composition of claim 1, comprising calcium
carbonate.
9. The membrane composition of claim 1, wherein the flame retardant
comprises calcium carbonate.
10. The membrane composition of claim 8, wherein the calcium
carbonate comprises at least 25 wt % of the membrane
composition.
11. The membrane composition of claim 1, wherein the amount of
flame retardant, ultraviolet stabilizer and pigment comprises at
least 25 wt % of the membrane composition.
12. The membrane composition of claim 1, wherein the amount of
propylene copolymer in the combination (iii) of a propylene
copolymer and an ethylene copolymer comprises from 30 to 70 wt %
based on the weight of the combination of copolymers.
Description
FIELD OF INVENTION
Formulations are provided which are useful in roofing applications.
Linear low density polyethylene is blended with thermoplastic
olefin (TPO) polymers, which blend can be used to prepare a roofing
membrane of enhanced properties.
BACKGROUND OF THE INVENTION
Compositions and membranes comprising thermoplastic olefin (TPO)
polymers have found widespread use in the roofing industry for
commercial buildings. For roofing and other sheeting applications,
the products are typically manufactured as membrane sheets. The
sheets are typically sold, transported, and stored in rolls. For
roofing membrane applications, several sheets are unrolled at the
installation site, placed adjacent to each other with an
overlapping edge to cover the roof and are sealed together by a
heat welding process during installation. During transport and
storage, the rolls can be exposed to extreme heat conditions, such
as from 40.degree. C. to 100.degree. C., which can lead to roll
blocking of the rolls during storage in a warehouse. After
installation, the membranes can be exposed during service to a wide
range of conditions that may deteriorate or destroy the integrity
of the membrane. As such, a membrane is desired that can withstand
a wide variety of service temperatures, with a particular focus on
thermal stability.
Thermoplastic olefin roofing membranes require high flexibility
together with good mechanical stability at elevated temperatures,
and high weathering resistance. A number of proposals for
thermoplastic olefin films of this type are disclosed in the
following publications.
US 2006/0046084 describes a thermoplastic polyolefin roofing
membrane produced from a mixture of a polypro-pylene-based
elastomer (PBE) and polyolefin copolymers.
US 2010/0255739 describes a roofing membrane with a composition
comprising a propylene-based elastomer.
US 2010/0197844 describes a thermoplastic olefin membrane for use
in construction materials which comprises a polypropylene-based
elastomer.
PCT Publication WO 2010/0115079A1 is directed to roofing membranes
that contain compositions comprising a propylene based elastomer
and an impact propylene-ethylene copolymer. The propylene based
elastomer was Vistamaxx.TM. 6102.
PCT Publication WO 2014/001224A1 is directed to compositions
comprising 40 to 75 wt % of at least one polypropylene-based
elastomer and around 25 to 60 wt % of at least one random copolymer
of polypropylene. The polypropylene-based elastomers used in WO
2014/001224A1 were Vistamaxx.TM. 3980, 6102, and 6202.
PCT Publication WO 2014/040914A1 is directed to thermoplastic
mixtures that comprise at least one impact-resistant polypropylene
copolymer and at least one ethylene-1-octene copolymer, where the
weight ratio of impact-resistant polypropylene copolymer to
ethylene-1-octene copolymer is in the range of 35:65 to 65:35.
U.S. Patent Ser. No. 62/121,230, filed on Feb. 26, 2015, is
directed to a roofing membrane composition of a 10-50 wt % of a
propylene-based elastomer, 5-40 wt % of a thermoplastic resin, at
least one flame retardant, and at least one ultraviolet
stabilizer.
U.S. Pat. No. 9,434,827 discloses a composition which is useful in
roofing membranes that comprises on a polymer basis, from 40 to 75%
by weight of at least one propylene based elastomer; and 25 to 60%
by weight of at least one random polypropylene copolymer.
In traditional mixtures, an at least semicrystalline polyolefin
material such as polyethylene or polypropylene, which provides the
mechanical strength and resistance to temperature change, is mixed
with a flexible blend component. This flexible blend component is
miscible, or at least compatible, with the polyolefin. Flexible
blend components used to date include, ethylene-propylene-diene
rubber (EPDM), ethylene-n-alk-ene copolymers, and also
polypropylene-based elastomers. At present, the most common TPO
polymer used in roofing membranes is Hifax.TM. CA10A, which is a
polypropylene random copolymer matrix with EP rubber well dispersed
throughout the polypropylene phase. However, improvements and cost
efficiency are still needed.
There still remains a need for roofing membranes that demonstrate
flexibility at service temperatures, particularly elevated
temperatures. There is also a need for more economical roofing
membranes which can meet such elevated temperature
requirements.
SUMMARY
A polymer blend composition comprising a propylene polymer having
from 10-60% crystallinity, a linear low density polyethylene, a
propylene copolymer; and an ethylene copolymer. In one embodiment,
the polymer blend composition comprises 15-75 wt % of the propylene
polymer, 30-50 wt % of the linear low density polyethylene, and 5
to 20 wt % of the propylene copolymer and ethylene copolymer
combined.
In one embodiment, the linear low density polyethylene comprises a
butene comonomer.
In one embodiment, the propylene polymer comprises rubber dispersed
in the polypropylene.
The foregoing polymer blends comprising a linear low density
polyethylene are useful in preparing a roofing membrane. The
roofing membrane would be prepared from a membrane composition
comprising a polymer blend of the present invention in an amount
ranging from 40 to 75 wt % of the composition, and will generally
include additives, e.g., at least one flame retardant, at least one
ultraviolet stabilizer and at least one pigment.
Among other factors, it has been surprisingly discovered that
combining linear low density polyethylene with a thermoplastic
polyolefin (TPO), e.g., the propylene polymer, an economical TPO
membrane with improved high temperature thermal stability can be
obtained. This is particularly achieved using the present polymer
blends, and this is achieved without modifying or changing the
stabilizer package. Adding the linear low density polyethylene to
the formulation has also been discovered to provide some processing
advantages.
DETAILED DESCRIPTION
Liner low density polyethylene (LLDPE) is well known in the polymer
industry and is readily available commercially. Linear low-density
polyethylene is a substantially linear polymer (polyethylene), with
significant numbers of short branches, commonly made by
copolymerization of ethylene with longer-chain olefins. Linear
low-density polyethylene differs structurally from conventional
low-density polyethylene (LDPE) because of the absence of long
chain branching. The linearity of LLDPE results from the different
manufacturing processes of LLDPE and LDPE. In general, LLDPE is
produced at lower temperatures and pressures by copolymerization of
ethylene and such higher alpha-olefins as butene, hexene, or
octene. The copolymerization process produces an LLDPE polymer that
has a narrower molecular weight distribution than conventional LDPE
and in combination with the linear structure, significantly
different rheological properties.
The production of LLDPE is initiated by transition metal catalysts,
particularly Ziegler or Philips type of catalyst. The actual
polymerization process can be done either in solution phase or in
gas phase reactors. Usually, octene is the comonomer in solution
phase while butene and hexene are copolymerized with ethylene in a
gas phase reactor. LLDPE has higher tensile strength and higher
than impact and puncture resistance than does LDPE. It is very
flexible and elongates under stress. It can be used to make thinner
films, with better environmental stress cracking resistance. It has
good resistance to chemicals. It has good electrical
properties.
The present invention provides an economical polymer blend that is
useful in roofing membranes that exhibits excellent high
temperature thermal stability as well as reduced tackiness. These
advantages are unprecedented and offer the industry a solution to
its quest for a more economical yet better performing roofing
membrane. These advantages have been discovered by combining linear
low density polyethylene with the more traditional thermoplastic
polyolefin polymers. The linear low density polyethylene
substitutes for some of the polyolefin polymers used in
conventional roofing membrane polymer blends in a manner which
allows phase stability. Maintaining phase stability is important,
otherwise the physical properties and stability of the finished
article are adversely affected. To the contrary, the right balance
of linear low density polyethylene has been found to insure phase
stability, without changing or modifying the stabilizer package,
while also providing a final product of improved performance. The
improved performance is particularly evident in thermal stability,
and maintaining that thermal stability over time.
In one embodiment, provided is a polymer blend composition
comprising linear low density polyethylene, a TPO polymer, i.e., a
propylene polymer (preferably having rubber dispersed therein), and
a combination of a compatibilizers comprising a polypropylene (PP)
matrix copolymer and a polyethylene (EP) matrix copolymer.
The most popular TPO resin used today for single ply roofing
membranes is an in-reactor blend resin that has a minor amount of
polypropylene copolymer as the matrix phase and
ethylene/polypropylene rubber as the majority phase well dispersed
in the polypropylene. The rubber phase is so fine and uniformly
distributed that it cannot be made by any conventional mechanical
mixing. Due to this unique morphology, it gives good mechanical
properties yet maintains its flexibility that is preferred by the
roofers for installation convenience.
This unique morphology, i.e., fine rubber distributed uniformly in
the polypropylene matrix, can be maintained even when alternative
polyolefin resins like those off-the-shelf are added to this
in-reactor grade resin. The linear low density polyethylene
(LLDPE), preferably with butene as its comonomer, can be used to
partially replace the in-reactor resin. The LLDPE is generally
softer than most polypropylene resins made by the Ziegler-Natta
process. Also, LLDPE is tough. Compatibility is always an issue
since LLDPE is polyethylene based and the TPO matrix is
polypropylene based. It has been surprisingly discovered, however,
that compatibility can be achieved by using a combination of
compatibilizers, i.e., a polypropylene copolymer and a polyethylene
copolymer. The resulting blend is compatible so the blend is stable
under high temperature and long term aging. The preferred
compatibilizers are metallocene made polypropylene and polyethylene
copolymer elastomers. There are two types of random copolymers made
by metallocene technology: polypropylene and polyethylene
elastomers. The common grades in the market are Engage.TM. or
Exact.TM. for the polyethylene copolymer and Versify.TM. and
Vistamaxx.TM. for the polypropylene copolymer. One popular grade
in-reactor resin used in the TPO roofing industry is Hifax CA10A
made by Equistar.
In general, the polymer blend of the present invention comprises
four components. Linear low density polyethylene (LLDPE) is one
component, and is readily available. LLDPE is commercially
available from chemical companies such as Exxon Mobil Corporation,
The Dow Chemical Company, LyondellBasel Industries N.V., Saudi
Basic Industries Corporation (SABIC), Borealis AG, Formosa Plastics
Corporation, U.S.A. (Formosa Plastics), China Petroleum &
Chemical Corporation (Sinopec Corporation), INEOS Group AG, Chevron
Phillips Chemical Company LLC, NOVA Chemicals Corporation, Sasol
Limited, and Braskem S.A.
While LLDPE is prepared by copolymerization of ethylene and
alpha-olefins, for the purposes of the present invention it is most
preferred that butene is the comonomer. It has been discovered that
the best performance and processing characteristics are achieved
when the LLDPE is prepared with butene as the comonomer.
Examples of suitable LLDPE resins, with butene comonomer, is
Dow.TM. DFDA-7047 NT7, available from Dow Chemical Company of
Midland, Mich. Chevron Philips 6109CL can also be used
successfully. In general, the LLDPE has a density of 0.915 to 0.920
g/cm.sup.3, and in another embodiment, from 0.916 to 0.918
g/cm.sup.3.
The amount of LLDPE used in the polymer blend composition of the
present invention ranges from 30-50 wt %. In another embodiment,
the amount ranges from 35 to 45 wt %, based on the total weight of
the polymer blend.
The second component is a propylene polymer having a crystallinity
of from 10-60%. Such resin components are well known. The propylene
polymer can be a random copolymer, an impact polymer, or
homopolymer. The random propylene polymer generally exhibits a
crystallinity of from 15-40%. The impact propylene polymer
generally exhibits a crystallinity of from 15-40%. The propylene
homopolymer can have a crystallinity of from 10-60%.
In one embodiment, the propylene polymer having a crystallinity of
from 10-60% is a propylene polymer having rubber dispersed therein.
The rubber can be any suitable buffer, but is generally EP rubber
(ethylene/propylene rubber). EDM rubber (ethylene/propylene/diene
monomer) can also be used.
Such polymers are well known. For example, Hifax.TM. CA10A,
available from LyondellBasel Industries of Arlington, Va. The Hifax
CA10A resin is a polypropylene matrix with EP rubber as the
majority phase, the rubber well dispersed in the polypropylene. The
rubber phase is finely and uniformly distributed throughout the
polypropylene phase. The polypropylene phase is a random copolymer
of polypropylene/polyethylene. Another commercial and useful
propylene polymer having rubber dispersed therein is available from
ExxonMobil Chemical Company under the tradename ExxonMobile.TM.PP.
One specific product is ExxonMobil.TM.PP7032. Another suitable TPO
for roofing membranes is Ineos TOOG-OO, available from Ineos
Olefins and Polymers, U.S.A.
The amount of the propylene polymer component in the polymer blend
generally ranges from 15 to 75 weight percent, based on the weight
of the blend. In one embodiment, the amount ranges from 20 to 50
weight percent. The propylene polymer component generally has a
crystallinity of from 10-60%, more likely 15 to 40%. The propylene
polymer component generally has a density that ranges from 0.87 to
0.92 g/cm.sup.3, with a density in the range of from 0.88 to 0.91
in one embodiment. The melt flow rate of the propylene polymer
component is generally in the range of from 0.5 to 20 g/10 min, and
in one embodiment the melt flow ranges from 0.5 to 5.0 g/10 min. A
melt flow rate in the range of from 0.6 to 4.0 g/10 min is
exhibited in one embodiment.
The third component is a propylene copolymer, generally a
propylene/ethylene copolymer having a polypropylene matrix.
This third component is generally used as a compatibilizer in the
blend, to aid in maintaining the blend and maintaining phase
stability. The ethylene content of the copolymer can vary.
Suitable propylene copolymers that can be used as a compatibilizer
are commercially available, and include Vistamaxx.TM. copolymers
from ExxonMobil Chemical Company. For example, Vistamaxx.TM. 6102
or 6202 may be used. Infuse.TM. olefin copolymers available from
Dow Chemical and Engage.TM. polyolefin elastomers from Dow Chemical
can also be successfully used. The polypropylene copolymer
generally has a density from 0.860 to 0.900 g/cm.sup.3 and a melt
flow rate of 1-25 g/10 min.
The fourth component is an ethylene copolymer, generally an
ethylene/propylene copolymer having a polyethylene matrix. This
fourth component is generally used as the second compatibilizer in
the blend. It has been found that the use of these two copolymers,
the third and fourth component, is important to maintaining phase
stability. Without the combination of these two specific
compatibilizers, good results with regard to phase stability are
not achieved.
Suitable ethylene copolymers that can be used as a compatibilizer
are commercially available, and include Engage.TM., available from
Dow Chemical. Another copolymer is the ethylene alpha olefin
copolymer Exact.TM., available from ExxonMobil Chemical. In
general, the ethylene copolymer has a density in the range of from
0.860 to 0.915 g/cm.sup.3, and a melt flow rate in the range of
about 0.5 to 5.0 g/10 min.
In one embodiment, the third and/or fourth components have been
prepared using a metallocene catalyst system. This is preferred.
The combination of the two copolymers is generally present in the
polymer blend composition in an amount ranging from 5 to 20 wt %,
based on the total weight of the blend. In one embodiment, the
amount ranges from 8 to 15 wt %. The relative ratio of the two
copolymer compatibilizers depends on the desired viscosity or flow
properties of the blend. In general, either component can be
present in an amount ranging from 30 to 70 wt % based on the weight
of the combination of copolymers. In one embodiment, the propylene
copolymer comprises about one third of the combination and the
ethylene copolymer about two thirds of the combination of
components.
The blend of polymers can be prepared by physically blending the
different components. The blend is therefore a combination of
polymer components that have already been formed and recovered
before mixing or otherwise combined. The blending can also occur
somewhat in solutions, miscible carriers, or by melt blending. The
resulting blend is a multiphase polymer composition.
The balance of components in the blend is important because
polypropylene and polyethylene will not maintain phase stability if
the mix is not balanced. Instead, regions of polypropylene and
polyethylene will form, which will affect the physical properties
and stability of the finished article adversely. However, by
maintaining the components in the range of from 30 to 50 wt %
LLDPE; 15 to 75 wt % of the polypropylene component and 5 to 20 wt
% of the combination of propylene and ethylene copolymer
compatibilizers, a polymer blend including HDPE is obtained which
maintains phase stability and provides even improved heat
stability. Cost efficiency is also realized by the present blend,
while still achieving improved performance characteristics.
The polymer blend can also contain a random olefin polymer, such as
a random polypropylene polymer. Such an addition can be in the 0 to
18 wt % range. The addition is generally made to adjust the flex
modulus to a desired level.
Once the polymer blend has been achieved, and often pelletized, the
blend can be used to prepare a membrane for use in a roof.
Generally, a membrane composition is prepared where certain
additives and fillers are added to the polymer blend. In one
embodiment, at least one flame retardant, at least one ultraviolet
stabilizer and at least one pigment is added to the polymer blend.
This prepares a membrane composition of from 40-75 wt % of the
polymer blend, based on the weight of the entire membrane
composition, with the remaining components comprising at least one
flame retardant, ultraviolet stabilizer and pigment. The flame
retardant can be present, in one embodiment, in an amount ranging
from 20 to 40 wt %, and the pigment in an amount of about 5 wt %.
The pigment often used is TiO.sub.2.
As noted above, the compositions described herein can also
incorporate a variety of additives. The additives may include
reinforcing and non-reinforcing fillers, antioxidants, stabilizers,
processing oils, compatibilizing agents, lubricants (e.g.,
oleamide), antiblocking agents, antistatic agents, waxes, coupling
agents for the fillers and/or pigment, pigments, flame retardants,
antioxidants, and other processing aids known to the art. In some
embodiments, the additives may comprise up to about 60 wt %, or up
to about 55 wt %, or up to about 50 wt % of the roofing membrane
composition. In some embodiments, the additives may comprise at
least 25 wt %, or at least 30 wt %, or at least 35 wt %, or at
least 40 wt % of the roofing membrane composition.
In some embodiments, the roofing membrane composition may include
fillers and coloring agents. Exemplary materials include inorganic
fillers such as calcium carbonate, clays, silica, talc, titanium
dioxide or carbon black. Any type of carbon black can be used, such
as channel blacks, furnace blacks, thermal blacks, acetylene black,
lamp black and the like.
In some embodiments, the roofing composition may include flame
retardants, such as calcium carbonate, inorganic clays containing
water of hydration such as aluminum trihydroxides ("ATH") or
magnesium hydroxide. For example, the calcium carbonate or
magnesium hydroxide may be pre-blended into a masterbatch with a
thermoplastic resin, such as polypropylene, or a
polypropylene/polyethylene copolymer. For example, the flame
retardant may be pre-blended with a polypropylene, where the
masterbatch comprises at least 40 wt %, or at least 45 wt %, or at
least 50 wt %, or at least 55 wt %, or at least 60 wt %, or at
least 65 wt %, or at least 70 wt %, or at least 75 wt %, of flame
retardant, based on the weight of the masterbatch. The flame
retardant masterbatch may then form at least 5 wt %, or at least 10
wt %, or at least 15 wt %, or at least 20 wt %, or at least 25 wt
%, of the roofing composition. In some embodiments, the roofing
composition comprises from 5 wt % to 40 wt %, or from 10 wt % to 35
wt %, or from 15 wt % to 30 wt % flame retardant masterbatch, where
desirable ranges may include ranges from any lower limit to any
upper limit.
In some embodiments, the roofing composition may include UV
stabilizers, such as titanium dioxide or Tinuvin.RTM. XT-850. The
UV stabilizers may be introduced into the roofing composition as
part of a masterbatch. For example, UV stabilizer may be
pre-blended into a masterbatch with a thermoplastic resin, such as
polypropylene. For example, the UV stabilizer may be pre-blended
with a polypropylene or an impact polypropylene-ethylene copolymer,
where the masterbatch comprises at least 5 wt %, or at least 7 wt
%, or at least 10 wt %, or at least 12 wt %, or at least 15 wt %,
of UV stabilizer, based on the weight of the masterbatch. The UV
stabilizer masterbatch may then form at least 5 wt %, or at least 7
wt %, or at least 10 wt %, or at least 15 wt %, of the roofing
composition. In some embodiments, the roofing composition comprises
from 5 wt % to 30 wt %, or from 7 wt % to 25 wt %, or from 10 wt %
to 20 wt % flame retardant masterbatch, where desirable ranges may
include ranges from any lower limit to any upper limit.
Still other additives may include antioxidant and/or thermal
stabilizers. In an exemplary embodiment, processing and/or field
thermal stabilizers may include IRGANOX.RTM. B-225 and/or
IRGANOX.RTM. 1010 available from BASF.
The compositions described herein are particularly useful for
roofing applications, such as for thermoplastic polyolefin roofing
membranes. Membranes produced from the compositions may exhibit a
beneficial combination of properties, and in particular exhibit an
improved balance of flexibility at temperatures across a wide
range, along with stability at elevated temperatures such as those
from 40.degree. C. to 100.degree. C. The roofing compositions
described herein may be made either by pre-compounding or by
in-situ compounding using polymer-manufacturing processes such as
Banbury mixing or twin screw extrusion. The compositions may then
be formed into roofing membranes. The roofing membranes may be
particularly useful in commercial roofing applications, such as on
flat, low-sloped, or steep-sloped substrates.
The roofing membranes may be fixed over the base roofing by any
means known in the art such as via adhesive material, ballasted
material, spot bonding, or mechanical spot fastening. For example,
the membranes may be installed using mechanical fasteners and
plates placed along the edge sheet and fastened through the
membrane and into the roof decking. Adjoining sheets of the
flexible membranes are overlapped, covering the fasteners and
plates, and preferably joined together, for example with a hot air
weld. The membrane may also be fully adhered or self-adhered to an
insulation or deck material using an adhesive. Insulation is
typically secured to the deck with mechanical fasteners and the
flexible membrane is adhered to the insulation.
The following Examples are provided to further illustrate certain
embodiments of the present invention, but the Examples are not
intended to be limiting.
Examples
Several formulations were prepared for testing and comparison. No.
1 cap and No. 1 core only comprise one compatibilizer copolymer,
i.e., Dow Engage 8180--a polyethylene based copolymer
compatibilizer. No. 2 cap and No. 2 core exhibit the present
invention where a combination of compatibilizer copolymers are
present, i.e., Dow Engage 8180 and Vistamaxx 6202 (a polypropylene
copolymer compatibilizer). A control TPO was also run.
The formulations are provided in the Table below. The formulations
were tested for tensile, tear and flexibility, as well as aging
characteristics. The results are in the Table below.
In the Table formulations, magnesium hydroxide (MAH) is the flame
retardant, white concentrate is polyolefin blended with highly
loaded titanium dioxide. Black concentrate is a carbon black based
composition.
Aging Cycle survived is determined by a rheological method that can
quantify the chain degradation. The UV/Heat degradation test was
conducted as follows:
For the cap ply: the molded sample was clamped in a Xenon Arc
radiation chamber for 2 days. After that, the sample was taken out
of the frame and put it in the 275.degree. F. oven for 5 days.
These two combined processes in a week is called 1 cycle.
For the core ply: a sample was put in the 275.degree. F. oven for a
week to complete a one week cycle.
TABLE-US-00001 TABLE No. 1 No. 1 No. 2 No. 2 TPO Formulations cap
core cap core Equistar CA10A 26 23.5 Ineos T00G-00 33 31.5 Dow
DFDA-7047 35 33 35 32.7 Vistamaxx 6202 6 2.7 Dow Engage 8180 5.5 8
5.5 4.7 Total rPP 7238 7 Magnesium hydroxide 20.4 20.4 20.4 20.3
White concentrate 4.5 3.2 4.5 3.5 Black Concentrate 1.8 1
Stabilizer package 1.6 0.6 UV concentrate 5.1 AO concentrate 3.6
Modulus from DMA, Pa 13.5E9 12.7E9 9.5E9 12.5E9 Tensile Strength,
psi 2032 1665 3810 1786 Tensile elongation, % 745 685 909 648 Die-C
Tear, (lb/in) 406 407 448 406 Cycles survived after 6 wks 5 wks 6
wks 6 wks UV/Heat Degradation
The No. 2 cap and core formulations exhibited improved tensile,
tear and flexibility in general, as well as equal or improved aging
characteristics. The same improvements were also exhibited compared
to a typical TPO formulation having no LLDPE.
Overall, the present polymer blend decreases the cost of roofing
membranes. An economical alternative is thereby provided. The
processing advantages also allow improved manipulation and more
efficient processing. The quite surprising improved properties in
heat stability, tensile, tear and flexibility most importantly lead
to a better final product. Because of the performance
characteristics, the roof will exhibit a longer life and better
weatherability. The heat stability also allows for improved welding
of the roofing membranes. Better welding also translates into a
better roof, both in function and life. The seams will last longer
and not pop-up because of the better seam welds. The present
polymer blend provides a more economical and better roof membrane,
which in turn provides a better roof.
While the foregoing is directed to embodiments of the present
invention, other and further embodiments of the invention may be
devised without departing from the basic scope thereof, and the
scope thereof is determined by the claims that follow.
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